With the advance in science, communications technology is rapidly developed. 5th generation mobile networks (hereinafter “5G”) can effectively increase data transmission rate, reduce delay, saving more energy, decrease cost and expand system capacity, so the advanced wireless technology has become the major development trend for many countries in the word. 5G is mainly applied in low frequency band (less than 6 GHz) or millimeter wave band, and phased array systems are one of the important technologies of the applications in millimeter wave band.
Phase shifters are one of the important components of a phased array system, so the design of the phase shifters will significantly influence the beam forming ability of the phased array system. The applicable frequency bands of 5G may include 28 GHz, 39 GHz, etc.
The characteristics of a phase shifter can be evaluated via RMS phase error and RMS gain error. In general, a 4-bit phase shifter needs 4 phase shifting units of different angles. 16 different phase statuses can be generated by turning on or off the phase shifting units.